Manufacturing of large oblong composite structures is by nature space consuming. Furthermore, this problem is enhanced as even a minor change in the structure, e.g. only relating to one end of the structure, commonly requires a complete, separate mould.
Wind turbine blades of fibre-reinforced polymer are usually manufactured as shell parts in moulds, where the top side and the bottom side of the blade profile (typically the pressure side and suction side, respectively) are manufactured separately by arranging glass fibre mats in each of the two mould parts. Afterwards, the two halves are glued together, often by means of internal flange parts. Glue is applied to the inner face of the lower blade half before the upper blade half is lowered thereon. Additionally, one or two reinforcing profiles (beams) are often attached to the inside of the lower blade half prior to gluing to the upper blade half.
The shell parts for the wind turbine blade are typically manufactured as fibre composite structures by means of VARTM (vacuum assisted resin transfer moulding), where liquid polymer, also called resin, is filled into a mould cavity, in which fibre material has been priorly inserted, and where a vacuum is generated in the mould cavity, hereby drawing in the polymer. The polymer can be thermoset plastic or thermoplastics.
Vacuum infusion or VARTM is a process used for moulding fibre composite mouldings, where uniformly distributed fibres are layered in one of the mould parts, the fibres being rovings, i.e. bundles of fibre bands, bands of rovings, or mats, which are either felt mats made of individual fibres or woven mats made of fibre rovings. The second mould part is often made of a resilient vacuum bag, and is subsequently placed on top of the fibre material. By generating a vacuum, typically 80% to 95% of the total vacuum, in the mould cavity between the inner side of the mould part and the vacuum bag, the liquid polymer can be drawn in and fill the mould cavity with the fibre material contained herein. So-called distribution layers or distribution tubes, also called inlet channels, are used between the vacuum bag and the fibre material in order to obtain as sound and efficient a distribution of polymer as possible. In most cases, the polymer applied is polyester or epoxy, and most often the fibre reinforcement is based on glass fibres or carbon fibres.
From DE 19833869 C1 it is known to provide a mould for wind turbine blades in a number of sections. However, the document is silent about how to ensure a smooth transition between the mould sections. Likewise, it is not discussed how to ensure that alternative mould sections, e.g. corresponding to different blade tips, are made to fit a given mid section.
Therefore, it is an object of the invention to obtain a new modular mould system, which overcomes or ameliorates at least one of the disadvantages of the prior art or which provides a useful alternative.